Hexafluoroisopropanol (hereinafter hexafluoroisopropanol may be expressed as “HFIP” in this specification) is produced in large quantities as a solvent showing specific solubility for polymers and as an intermediate for the production of an inhalation anesthetic “sevoflurane”. HFIP is generally produced through hydrogenation of hexafluoroacetone (hereinafter this may be expressed as “HFA” in this specification), and various methods have been proposed depending on the combination of the form of the starting material HFA, its reaction mode, the types of the reducing agent and the catalyst, etc.
As a gas-phase method, there are known a method of hydrogenation of HFA with hydrogen (H2) in the presence of an alumina-supported palladium catalyst (Pd/Al2O3) (Patent Publication 1) or in the presence of an activated carbon-supported palladium catalyst (Pd/C) (Patent Publication 2), and a method of hydrogenation of HFA hydrate in the presence of a nickel catalyst or an alumina-supported palladium catalyst (Patent Publication 3).
Regarding the method for producing HFIP by hydrogen gas in a liquid phase, there are known a method of using HFA hydrate and a method of using HFA anhydride. As the method of using the anhydride, a method of reacting it over a period of 6 hours at 110° C. to 150° C. under a pressure of 20.0 to 90.0 MPa (200 to 900 atmospheres) using platinum oxide as a catalyst (Patent Publication 4) and the like have been reported.
On the other hand, the method of hydrogenating HFA hydrate in a liquid phase includes a method of reacting it over a period of 3.5 hours at 70° C. to 75° C. under a pressure of 0.35 to 0.7 MPa (3.5 to 7 kg/cm2) using palladium/carbon as a catalyst (Patent Publication 5), and a method of reacting it over a period of 6 hours at 100° C. under a pressure of 0.5 MPa (5 kg/cm2) using palladium/Al2O3 as a catalyst (Patent Publication 6), etc.
As a method using a reducing agent other than hydrogen (H2), there have been reported a method of reducing HFA anhydride, using sodium borohydride as a reducing agent in a methanol solvent, and similarly a method using lithium aluminum hydride, calcium hydride, sodium hydride or the like as a reducing agent in an oxygen-containing solvent such as diethyl ether, methanol, isopropanol, tetrahydrofuran or the like (Patent Publication 4).
According to Patent Publication 7, hydrogenation of HFA hydrate through contact with hydrogen in the presence of a palladium catalyst produces an excessively-hydrogenated product, 1,1,1-trifluoroacetone (TFA), in addition to the target product HFIP. The TFA is said to be difficult to be separated through distillation, since the boiling point thereof is close to that of the target product HFIP. However, Patent Publication 7 reports that, by using “a combined catalyst of palladium and ruthenium” as the hydrogenation catalyst, the target product HFIP can be produced in a sufficient selectivity, that, even when TFA is produced in a small amount, this compound can be readily converted into 1,1,1-trifluoroisopropanol (an easily separable compound, hereinafter this may be abbreviated as TFIP), and that, accordingly, after the reaction, it has become greatly easy to obtain hexafluoroisopropanol having a high purity (see the following).

On the other hand, Patent Publication 8 reports that, when a crude HFIP obtained through hydrogenation of HFA in the presence of a catalyst is treated with an organic amine compound, hardly-separable TFA can be removed out of the system in the form of “an associate with the amine compound”, and through subsequent distillation, HFIP not substantially containing TFA can be obtained.
Further, it is reported that, when HFA is hydrogenated through contact with hydrogen gas at −20 to 60° C. in the presence of a metal catalyst such as palladium, ruthenium or the like or a catalyst carrying the metal, in a hydrogen fluoride solvent, HFIP not substantially containing excessively-hydrogenated 1,1,1-trifluoroacetone can be obtained (Patent Publication 9).
Regarding the production of hexafluoroacetone (HFA) that is the starting material for producing HFIP, there is known a method of epoxidating hexafluoropropene (Patent Publication 10), followed by isomerizing the resultant epoxy compound in the presence of a catalyst to obtain HFA (Patent Publication 11). There is also known a method of chlorinating acetone to give hexachloroacetone (Patent Publication 12), followed by subjecting the resultant hexachloroacetone to a substitutive fluorination with hydrogen fluoride in the presence of a chromium-supported activated carbon catalyst or the like (Patent Publication 13).
As described above, HFIP is extremely important as a starting material for producing an inhalation anesthetic sevoflurane (chemical name: fluoromethyl-1,1,1,3,3,3-hexafluoroisopropyl ether). Specifically, as illustrated in Patent Publication 14, an inhalation anesthetic sevoflurane can be produced by adding concentrated sulfuric acid and hydrogen fluoride to paraformaldehyde, then heating the resultant mixture at a predetermined temperature and dropwise adding HFIP thereto.